Preparation of di(arylamino) anthraquinones



Patented Mar. 28, 1939 PATENT OF'Fi-CE PREPARATION OF DI ARYLAIVIINO')ANTHRAQUINONES Wilbert A. Herrett, Hamburg, N. Y., assignor to NationalAniline & Chemical Company, Inc., New York, Y., a corporation of NewYork No Drawing.

Application October 28, 1936,

Serial No. 108,093

17 Claims.

The present invention relates to a method for the preparation oflA-diarylamino derivatives of anthraquinone from quinizarine, leucoquinizarine or a mixture of the two, and more particularly to a methodfor the preparation of the 1,4- di-p-toluido derivative of anthraquinonecommonly known as quinizarine green.

It is an object of the present invention to provide a process wherebydi(arylamino)anthraquinones may be prepared from quinizarine, leucoquinizarine, or a mixture of the two, and an arylamine in high yields,and of excellent quality.

Cther objects of the invention will in part be obvious and will in partappear hereinafter.

It is known that diarylamino derivatives of anthraquinone can be formedby condensing quinizarine, leuco quinizarine, or a mixture of the twowith an arylamine in the presence of a condensation agent and in aninert medium consisting of a chlorinated hydrocarbonof the benzeneseries. Ordinarily this condensation is carried out with the aid of areducing agent, particularly when quinizarine is employed as thestarting material. The reaction is conducted at an elevated temperature,and is generally carried out in the presence of air whereby the leucodi(arylamino)anthraquinone which is initially formed is oxidized to thequinoid form.

It has been discovered in accordance with the present invention that theyield and quality of di(arylamino)anthraquinones obtained with the useof this. general process can be increased by subjecting the reactionmass at the completion of the condensation to an auxiliary oxidationtreatment. This auxiliary oxidation treatment is preferably effected byheating the reaction mass with a small amount of an aromatic nitrocompound, such as, for example, nitrobenzene, at an elevatedtemperature, preferably between about 120 and 140 0., for a short periodof time.

In the practice of the present invention in accordance with one methodof procedure, quiniz arine, leuco 'quinizarine, or a mixture of the two(referred to generically herein as a quinizarine compound) is condensedwith an arylamine in the presence of an acetic acid condensing agent andof monochlorbenzene, which serves as an inert medium for the reaction,and the product is recovered by oxidizing with air supplemented by 50.an auxiliary oxidation treatment, preferably with an aromatic nitrocompound. In general, and

particularly when quinizarine is employed as the starting material, thereaction is also carried out with a reducing agent such as, for example,finely divided zinc.

i2 C., so as to drive 01f substantially all of the water added in theacetic acid solution while avoiding any substantial condensation takingplace between the arylamine and the quinizarine. The mixture is raisedto an elevated temperature, for example, between about to about C. forthe period of time required to complete the condensation while allowingwater vapor to escape. The reaction is carried out in contact with theair so as to oxidize the major portion or the leuco di(arylamino)anthraquinone, which is initially formed in the reaction, to the quinoidform. To complete the oxidation of the leuco di(arylamino)anthraquinone,a small amount of an oxidizing agent such as, for example, an aromaticnitro compound, e. g., nitrobenzene, is introduced into the reactionmass at or near to the completion of the condensation reaction, and themixture is agitated and heated at a temperature of about 120 to about140 C. for a short period of time. At the completion of this auxiliaryoxidation step, the di(arylami no) anthraquinone may be recoveredfromrthe reaction mass by cooling and crystallizing and filtering offthe thus formed crystals. To assist in' the crystallization andseparation of the di- (arylamino)anthraquinone from the reaction mass,the mass, prior to cooling, may be diluted with an additional amount ofmonochlorbenzene.

By employing an auxiliary oxidation treatment with an aromatic nitrocompound, it has been found to be possible to increase materially theyields of the di(ary1amino)anthraquinone obtainable in the process. Thiswas not to be anticipated since the reaction mass prior to thisauxiliary oxidation has been subjected to the oxidizing action of air,usually by carrying out the reaction in the presence of air. Withoutlimiting the invention to any theoretical explanation, it would seem theimproved results ob- 'tainable are probably due in some measure tothefacts that in the preparation of quim'zarine green and similardiarylamino derivatives of anthraquinone from quinizarine the operatingconditions employed when air is relied upon entirely for oxidizing theleuco di(arylamino)anthraquinone in the reaction mass fail to produceuniform oxidation since the supply of air coming in contact with themixture varies in successive operations, and that small quantities ofthe leuco di(arylamino) anthraquinone in the reaction mass may be insuch stable condition as not to be oxidizable by the action of air andremain in the inert medium when the di(arylamino)anthraquinone isseparated therefrom. The auxiliary oxidation treatment with an aromaticnitro compound at the end of the reaction appears to eliminate thevariation in the extent of oxidation encountered in the prior proceduresand also to oxidize the more resistant forms of the leuco di-(arylamino)anthraquinone to the quinoid form.

Monochlorbenzene is a highly efficient inert medium for the reactionunder consideration being not only valuable in so far as the yieldsobtainable in relation to the amounts of quinizarine and arylamineemployed are concerned, but also being of advantage in that relativelysmall amounts of the monochlorbenzene may be employed as the inertmedium for the reaction. Further, by employing monochlorbenzene .as theinert medium for the reaction it is possible to reduce the highesttemperature of the reaction to between about 120 and about 140 C.

Aqueous solutions of acetic acid of the foregoing concentrations arevaluable assistants in the present reaction being equivalent in effect,with respect to the yields obtainable, to other condensing agents overwhich they represent a material advantage in regard to economy ofoperation. It is surprising that these aqueous acetic acid solutionsshould be of high efficiency in this connection since glacial aceticacid is of relatively low efficiency when employed in the reaction.

In order that the present invention may be more fully understood,reference should be had to the following example which illustrates apreferred manner of carrying out the process of the invention. It willbe understood, however, that the invention is not limited to the detailsof this example. The parts are by weight, and the temperatures indegrees centigrade.

Emample.-In a suitable vessel equipped with an agitator, a mixture of 50parts of quinizarine, 62 parts of para-toluidine, 100 parts ofmonochlorbenzene, .and 5.1 parts of zinc dust is heated at 58 to 60.Then 9.6 parts of per cent acetic acid are added. Due to the heat ofreaction between the zinc, acetic acid, and quinizarine to formleucoquinizarine, the temperature of the mixture rises to between 70 and80. The resulting mixture containing para-toluidine, quinizarine, andleuco-quinizarine, is heated to a temperature of and then slowly to atemperature between 98 and 102 where it is maintained untilsubstantially all of the free water which is present has distilled offtogether with a portion of the monochlorbenzene. During this period,practically no condensation takes place between the quinizarinecompounds and the para-toluidine. After the free water has beenexpelled, the temperature is raised to 132 to 135, and is held at thispoint until the condensation between the quinizarine compounds and thepara-toluidine to form 1,4-di(p-toluido)anthra quinone is practicallycompleted. This ordinarily requires about 5 to 6 hours. During thisstep, the water formed in the condensation is allowed to'escape. To theresulting mass, about 1 to 2 parts of nitrobenzene are added and themixture is agitated at a temperature of 128 to 130 for about half anhour. It is then diluted with parts of monochlorbenzene and is allowedto cool, whereby crystals of l, l-di(p-toluidolanthraquinone(quinizarine green) are precipitated. The precipitated crystals ofquinizarine green are separated as a filter cake by filtration. Theyield of quinizarine green is about 10 per cent greater than thatobtained by proceeding in the above manner, but omitting the addition ofthe nitrobenzene and extra heating.

With the use of an analogous process to that described in the example,other diarylamino derivatives of anthraquinone may be prepared fromquinizarine by employing in place of p-toluidine,

any other of the arylamines known in this connection, such as, forexample, aniline and its homologues, naphthylamines, etc. These aryl-vamines are preferably employed in the proportions of at least two molsof the arylamine to each mol of quinizarine compound. For example, forreaction with 100 parts of quinizarine, there should preferably beemployed at least 89 parts of p-toluidine.

It will be understood that the amount of aromatic nitro compound whichis employed as an auxiliary oxidant at the end of the condensationprocedure will vary with the volume of the reaction mass and thephysical conditions under which the condensation is effected. Amongthese conditions are the type of vessel employed, the extent to whichthe mixture is agitated, .and the amount of air with which the mixtureis allowed to come in contact. In general, under normal operatingconditions, it has been found that an amount of nitro compoundequivalent to a few per cent, e. g., four per cent, and more often aboutone per cent, of nitrobenzene based on the weight of quinizarineemployed in the reaction is sufficient to cause substantially completeoxidation of the leuco di(arylamino)anthraquinone in the reactionmixture. It will be understood, of course, that an excess of an aromaticnitro compound may be employed but ordinarily the use of an excess is ofno advantage in regard to the yields obtainable. As indicated above, theauxiliary oxidant may be any suitable aromatic nitro compound, such as,for example, nitrobenzene, nitrotoluene, nitrochlorbenzene, nitraniline,nitrotoluidine, etc.

The auxiliary oxidation with the aromatic nitro compound is affected bythe temperature maintained during this step, and it has been found thatthe most effective temperature range is that employed for the aminationreaction. Thus, this auxiliary oxidation is preferably carried out inaccordance with the present invention at a temperature between about andabout C., which is also the preferred temperature range for conductingthe amination reaction.

The amounts of the other materials used in the process of the aboveexample may be varied. A feature of the invention resides in the factthat by employing monochlorbenzene as the inert medium for the reactionit is possible to use relatively small amounts of this material. Forexample, based on 100 parts of quinizarine charged to the reactionvessel, efficient results may be obtained in accordance with the presentinvention with the use of between about 80 and about 400 parts, andpreferably about 200 parts, of monochlorbenzene.

The aqueous solution of acetic acidused in the the leuco di(arylamine)anthraquinone is arine compound selected from and leuco quinizarine isconprocess of the present invention is preferably about an 80 per centaqueous solution. However, aqueous solutions of acetic acidvarying inconcentration from '70 per cent to 95 per cent acetic acid may be usedin the process with satisfactory results. The aqueous solution of aceticacid is preferably employed in such proportions as to provide from about14 parts to about 1'7 parts acetic acid for each 100 parts ofquinizarine.

' The present process is of particular advantage when quinizarine isemployed as the starting material. The process may be carried out,however, by starting with leuco quinizarine or a mixture of leucoquinizarine and quinizarine. Where leuco quinizarine is used, the amountof finely divided zinc employed in the reactionmay be reducedconsiderably and may even be eliminated. Where quinizarine is employedas the starting material the finely divided zinc is preferably employedin the proportions of about 7.6 parts to about 11 parts of zinc for each100 parts of quinizarine.

Since changes may be made in the above process without departing fromthe scope of the invention, the foregoing desciption should beinterpreted as illustrative and not in a limiting sense.

I claim:

1. In the method for the preparation of a di(arylamino) anthraquinone inwhich a quinizarine compound selected from the group consisting'ofquinizarine and leuco quinizarine is condensed with an arylamine to forma leuco di(arylamino) anthraquinone and the leuco di-arylamino)anthraquinone is oxdized to the di(arylamino) anthraquinone, theimprovement which comprises condensing the quinizarine compound with thearylamine in the presence of an acetic acid condensing agent andmonochlorbenzene, and subjecting the reaction mass to the oxidizingaction of an aromatic nitro compound.

2. In the method for the preparation of a di(arylamino)anthraquinone inwhich leuco quinizarine is condensed with an arylamine to form a leucodi(arylamino)anthraquinone and oxidized to the di(arylamino)anthraquinone, the improvement which comprises condensing leucoquinizarine with the arylamine in the presence of an acetic acidcondensing agent and monochlorbenzene, and subjecting the reaction massto the oxidizing action of an aromatic nitro compound of the benzeneseries.

3. In the method for the preparation of a di(arylamino)anthraquinone inwhich a quinizthe group consisting of quinizarine densed with anarylamine to form a leuco di(arylamino) anthraquinone and the leucodi-arylamino) anthraquinone is oxidized to the di-arylamino)anthraquinone, the improvement which comprises condensing thequinizarine compound with the arylamine in the presence of an aceticacid condensing agent and monochlorbenzene, and subjecting the reactionmass to the oxidizing action of nitrobenzene.

4. In the method for the preparation of 1,4- di(p-toluido) anthraquinonein which a quinizarine compound selected from the group consisting ofquinizarine and leuco quinizarine is condensed with p-toluidine to formleuco 1,4-di(ptoluido) anthraquinone and the leuco 1,4-di(ptoluido)anthraquinone is oxidized to 1,4-di(ptoluido)anthraquinone, theimprovement which comprises condensing the quinizarine compound withp-toluidine in the presence of an acetic acid condensing agent andmonochlorbenzene, and subjecting the reaction mass to the oxidizingaction of nitrobenzene. V

5. In the method for the preparation of a di(arylamino)anthraquinone inwhich a quinizarine compound selected from the group consisting ofquinizarine and leuco quinizarine is condensed with an arylamine to forma leuco di(aryl.- amino) anthraquinone and the leuco di(arylamino)anthraquinone is oxidized to the di-arylamino) anthraquinone, theimprovement which comprises heating a mixture containing the quinizarinecompound, arylamine, acetic acid, and monochlorbenzene to form initiallya leuco di(ary1amino)anthraquinone, oxidizing the leuco di(arylamino)anthraquinone in the reaction mass with air, and subjecting the reactionmass to the oxidizing action of an aromatic nitro compound.

6. In the method for the preparation of a di(arylamino) anthraquinone inwhich leuco quinizarine is condensed with an arylamine to form a leucodi(arylamino anthraquinone and the leuco di(arylamino)anthraquinone isoxidized to the di(arylamino)anthraquinone, the improve ment whichcomprises heating a mixture containing leuco quinizarine, the arylamine,acetic acid, and monochlorbenzene to form initially a leucodi(arylamino)anthraquinone, oxidizing the leuco di(arylamino)anthraquinone in the reaction mass with air, introducing into thereaction mass an aromatic nitro compound, heating the resulting mixtureto cause the aromatic nitro compound to oxidize remaining leucodi(arylamino) anthraquinone to the di(arylamin o) anthraquinone, andrecovering the di(arylamino)anthraquinone.

'7. In the method for the preparation of a di(arylamino)anthraquinone inwhich quinizarineis condensed with an arylamine of the benzene series inthe presence of a reducing agent to form a leuco di(arylamino)anthraquinone, and the leuco di(arylamino) anthraquinone is oxidized tothe di(aryla mino) anthraquinone, the improvement which comprisesheating a mixture containing quinizarine, the arylamine of the henzeneseries, finely divided zinc, an aqueous solution of acetic acidcontaining from about 70 per cent to about 95 per cent acetic acid, andmonochlorbenzene to form initially a leuco di(arylamino) anthraquinone,subjecting the leuco di- (arylamino) anthraquinone in to the oxidizingaction of air, introducinginto the resulting reaction mass a smallamount of an aromatic nitro compound of the benzene series, heating theresulting mixture, and recovering a di(arylamino) anthraquinone.

8. In the method for the preparation of a 1,4- di(arylamino)anthraquinone in'which quinizarine is condensed with an arylamine in thepresence of a reducing agent to form a leuco 1,i-di(arylamino)anthraquinone and the leuco 1,4-di(arylamino) anthraquinone is oxidizedto the 1,4- di(arylamino)anthraquinone, the improvement which comprisesheating a mixture containing quinizarine, the arylamine, finely dividedzinc and an aqueous solution of acetic acid containing from about '70 toabout 95 per cent acetic acid in an inert medium consisting ofmonochlorbenzene to a final temperature within the range about 120 toabout 140 C. in the presence of air to effect condensation between thequinizarine and the arylamine and to form a reaction mass containing aleuco 1,4-di(arylamino)anthraquinone and a1,4-di(arylamino)anthraquinone, introducing into the reaction mass asmall amount of an aromatic nitro compound, heating the resultthereaction mass arlyamine, finely-divided zinc, cent aqueous solution ofacetic acid, and monoperature between about 120 and about 140 C. andcontinuing the heating in the presence of air, to effect condensationbetween the quinizarine and the arylamine and to form a reaction masscontaining a leuco di(arylamino)anthraquinone and series in the presenceof a reducing agent to form a leuco di(arylamino)anthraquinone, and theleuco di(arylamino) anthraquinone is series, finely-divided zinc, aboutan 80 per cent aqueous solution of acetic acid, and monochlorbenzene asan inert medium to a final temperature between about 120 and about 140C., and continuing the heating in the presence of air, to eiTect acondensation between the quinizarine and the arylamine and to form areaction mass containing a leuco di(arylamino)anthraquinone and adi(arylamino)anthraquinone, introducing into the reaction mass a smallamount of an aromatic nitro compound of the benzene series, heating theresulting mixture at a temperature between about 120 C. and about 140 C.for a period of time sufiicient to cause the aromatic nitro compound tooxidize the leuco di(arylamino)anthraquinone to thedi(arylamino)anthraquinone, and recovering thedi(arylamino)anthraquinone. V

11. In the method for the preparation of a 1,4- di(a rylamino)anthraquinone in which quinizarine is condensed with an arylamineselected from the group consisting of aniline and its homologues in thepresence of a reducing agent to form a leuco1,4-di(arylamino)anthraquinone and the leuco1,4-di(arylamino)anthraquinone is oxidized to thedi(arylamino)anthraquinone, the improvement which comprises heating amixture containing quinizarine, the arylamine, zinc, an aqueous solutionof acetic acid containing from about 70 per cent to about 95 per centacetic acid, and monochlorbenzene to form leuco quinizarine, heating themixture to drive off water while avoiding condensation of the leucoquinizarine and the arylamine, then heating the mixture in the presenceof air at a temperature from about 120 to about 140 C., to effect acondensation between leuco 1,4-di(ary1amino)an'- 1,4-di(arylamino)anthraquinone, and recovering the 1,4-di(arylamino)- anthraquinone.

12. In the method for the preparation of a 1,4-

arylamine and to form a reactlon mass containing a leuco1,4-di(arylamino)anthraquinone and a 1,4-di (arylamino) anthraquinone,introducing into the reaction mass a small amount of an aromatic nitrocompound, heating the resulting mixture at a temperature between about120 and about 140 C. for a period of time sufiicient to oxidize theleuco 1,4-di(arylamino)anthraquinone to the 1,4-di(arylamino)anthraquinone, and recovering the 1,4-di(ary1amino)anthraquinone.

13. A method for the preparation of 1,4-di(ptoluido)anthraquinone, WhlChcomprises heating reducing agent, containing from about 70 per cent'toabout 95 per cent acetic acid, and monochlorbenzene to a finaltemperature of about 120 to about 140 C. in the di (p toluido)anthraquinone.

14; A method for the preparation of 1,4-di(ptoluido)anthraquinone, whichcomprises heating a mixture containng quinizarine, p-toluidine, zinc,anaqueous solution of acetic acid containing from about 70 per cent toabout 95 per cent acetic acid, and monochlorbenzene to a finaltemperature of about 120 to about 140 C. in the presence of air, toeffect a condensation between the quinizarine and the p-toluidine and toform a reaction mass containing leuco compound, temperature betweenabout 120 and about 140 C. for a period of time suflicient to oxidizethe leuco 1,4 di(p-toluido) anthraquinone to 1,4 di(p toluido)anthraquinone, and recovering 1,4-di(ptoluido) anthraquinone.

15. A method for the preparation of 1,4-di(ptoluido) anthraquinone whichcomprises heating a mixture containing 100 parts of quinizarine, at'

least 89 parts of p-toluidine, about 7.6 to about 11 parts of zinc, anaqueous solution of acetic acid containing from about '70 per cent toabout 95 per cent acetic acid in such proportions as to contain about 14to about 1'7 parts of acetic acid, and monochlorbenzene to a finaltemperature of about 120 to about 140 C. in the presence of air, toeffecta condensation between the quinizarine and the p-toluidine and toform a reaction mass containing leuco 1,4-di(p-toluido) anthraquinoneand 1,4- di(p-toluido) anthraquinone, introducing into the reaction massan amount of an aromatic nitro compound equivalent to 1 to 4 parts ofnitrobenzene, heating the resulting mixture at a temperature betweenabout 120 C. and about 140 C. for a period of time sufficient to oxidizethe leuco 1,4- di(p-toluido) anthraquinone to 1,4-di(p-toluido)anthraquinone, and recovering 1,4-di(p-toluido) anthraquinone.

16. A method for the preparation of 1,4-di(ptoluido) anthraquinone whichcomprises heating a mixture containing 100 parts of quinizarine, atleast 89 parts of p-toluidine, about 7.6 to about 11 parts of finelydivided zinc, an aqueous solution of acetic acid containing about 80 percent acetic acid in such proportions as to contain about 14 to about 1'7parts of acetic acid, and about 80 to about 400 parts ofmonochlorbenzene to a temperature adapted to drive off the water presentwhile avoiding substantial condensation of the quinizarine with thep-toluidine, then heating the mixture in the presence of air at atemperature of about 120 to about 140 C., to effect a condensationbetween the quinizarine and the p-toluidine and to form a reaction masscontaining leuco 1,4-di(p-toluido) anthraquinone and 1,4- di(p-to1uido)anthraquinone, introducing 1 to 4 parts of nitrobenzene into thereaction mass, heating the resulting mixture at a temperature betweenabout 120 and about 140 C. for a period of time sufficient to oxidizethe leuco 1,4-di(p-toluido) anthraquinone to1,4-di(p-toluido)anthraquinone, and recovering 1,4-di(ptoluido)anthraquinone.

17. A method for the preparation of 1,4-di(ptoluido)anthraquinone whichcomprises reacting a mixture containing about 50 parts of quinizarine,about 62 parts of p-toluidine, about 5 parts of finely divided zinc,about 9.6 parts of an 80 per cent aqueous solution of acetic acid, andabout 100 parts of monochlorbenzene to form leuco quinizarine in themixture, heating the resultin mixture at a temperature of about 100 C.until the water present is substantially driven off, then heating themixture in the presence of air at a temperature of 132 to 135 C., toeffect a condensation between the leuco quinizarine and the p-toluidineand to form a. reaction mass containing leuco 1,4-di(p-to1uido)anthraquinone and 1,4- di(p-toluido) anthraquinone, introducing into thereaction mass from 1 to 2 parts of nitrobenzene, heating the resultingmixture at a temperature of about 130 C. for about one-half hour tooxidize the leuco 1,4-di(p-toluido)anthraquinone to1,4-di(p-toluido)anthraquinone, and recovering 1,4-di(p-toluido)anthraquinone.

WILBERT A. HERRETT.

